Turbine engines, as well as other turbomachinery systems, benefit from confining and controlling the flowpath of heated gases. When heated gas passes across the turbine blades, work is extracted from the heated gas. Accordingly, the efficiency of the turbine engine is directly dependent on the proportion of heated gas passing across the turbine blades. It is desirable to increase the efficiency to produce more power from a given amount of fuel.
One way heated gases can flow around turbine blades, rather than across them, is by traveling through a radial gap. The radial gap is a space which exists between the tip of turbine blades and the surrounding shroud. A shroud is typically used to surround the turbine blades, confining the hot gases to the flowpath. The shroud is, in turn, supported by a support structure, and the two are coupled together. In addition to metals, ceramics can be used to form certain shrouds and shroud components. Unfortunately, ceramics and metals typically have different thermal expansion properties. As a result, when the turbine is operating at high temperatures, if a shroud and shroud support are composed of the dissimilar materials—such as a ceramic shroud with a metal shroud support, the shroud and shroud support tend to expand or grow at different rates. This can result in specific spacing requirements to accommodate the dissimilar growth rates.
Additionally, tolerances inherent in the manufacture of the components also introduce spacing requirements into the engagement. Both spacing requirements are typically addressed by adding space for clearance in the coupling arrangement between the shroud and shroud support. The increased space in the coupling arrangement, in turn, increases the size of the radial gap between the turbine blades and the shroud. Consequently, the efficiency of the engine is reduced. It would be beneficial to use a coupling assembly which can accommodate different expansion rates among the components without requiring an increase in the size of the radial gap. Additionally, it would be advantageous to use a coupling assembly which minimizes contributions to the radial gap size by the spacing required to accommodate manufacturing tolerances.